Observations of 1.4Hz quasi-periodic oscillations in CIR X-1.
Abstract
Cir X-1 was observed to vary by a factor of about 1000 during an Exosat observation made in August 1985. The power spectrum is about 1/f from about 10 to the -5th to about 0.02 Hz. Above 0.02 Hz the power spectrum steepens. In this paper, results from the interval in which the source flux increased to the maximum are presented. During this interval the source was highly variable on time-scales of greater than 1 s. The lack of high-frequency noise and the shape of the energy spectrum favor a model in which most of this variability is due to obscuration of the central source. Quasi-periodic oscillation (QPOs) were detected at a frequency of 1.4 Hz. There was no indication of a change in the peak frequency as the intensity varied by a factor of greater than 3. When compared to a previously published observation of Cir X-1, evidence is found that the QPO is bimodal with the low-frequency being independent of intensity.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- February 1988
- DOI:
- 10.1093/mnras/230.3.403
- Bibcode:
- 1988MNRAS.230..403T
- Keywords:
-
- Light Curve;
- Power Spectra;
- Satellite Observation;
- Stellar Oscillations;
- Astronomical Models;
- Exosat Satellite;
- Pulsars;
- X Ray Sources;
- Astrophysics